The fate of copper in flooded south Florida agricultural soils and its toxicological effects on the Florida apple snail, Pomacea paludosa

Agricultural sites have been acquired under the Comprehensive Everglades Restoration
Plan (CERP) for the creation of water storage areas. Copper desorption and toxicity to
the Florida apple snail (Pomacea paludosa) were investigated using soils from these
sites. Copper concentrations in II soils ranged from 5 to 234 mg/kg Cu dw, and when
flooded, resulted in overlying water Cu concentrations from 9 to 308 11g/L Cu. Juvenile
apple snails exposed to three flooded soils had high mortality and decreased growth
within 9 to 16 days in two ofthe three soils examined. To assess Cu toxicity to the apple snail at various life stages and water quality
parameters, 96 hour acute toxicity studies were conducted. Copper was more toxic to
juvenile than adult apple snails. Copper toxicity increased as pH decreased and
decreased as DOC increased. Hardness had no effect on Cu toxicity to the apple snail.
Copper toxicity was a function of organism age, DOC and pH.
Copper accumulation by juvenile and adult apple snails was determined for multiple
exposure pathways. For 28 days, juvenile snails were exposed to aqueous Cu and adult
snails were exposed to Cu contaminated soil, water and food. Whole body Cu in juvenile
snails increased with time. The mean Cu bioconcentration factor (BCF) for juvenile
snails was 1493. For adult snails, the dietary exposure pathway resulted in the highest
bioaccumulation factor (BAF). Most Cu accumulated in soft tissue.
During a chronic aqueous exposure, apple snails exposed to 8-16 flg /L Cu for 9 months
had high Cu accumulation and significantly reduced clutch production (8-16 flg /L) and
egg hatching (16 flg/L ). Chronic Cu exposure initially decreased growth in juvenile
snails, but growth rebounded by adulthood and snails appeared to acclimate to chronic Cu
exposure.
When apple snails with high tissue Cu were fed to redear sunfish (Lepomis microlophus)
Cu transfer was minimal, suggesting that the risk of trophic transfer (bioaccumulation) of
Cu from the snail to redear sunfish is low and that biomagnification is unlikely. It is
uncertain if other apple snail predators would be at risk for dietary Cu transfer.